Balloon angioplasty, a medical procedure by which an occluded or narrowed blood vessel is dilated and reopened using an inflatable balloon mounted on a catheter, was pioneered by Andreas Greuntzig in the 1970's. The coronary version of this new procedure, Percutaneous Transluminal Coronary Angioplasty (PTCA), soon became recognized as a highly effective method of treating diseased coronary artery disease. More recently, angioplasty has become a standard approach for treatment of renal artery stenoses. Percutaneous Transluminal Renal Angioplasty (PTRA), with its low rate of complications, has now largely replaced surgery as treatment for renal artery stenoses, which are common contributing factors in patients diagnosed with arterial hypertension, renal insufficiency, or cardiac insufficiency.
The basic angioplasty procedure usually involves percutaneously introducing a guiding catheter through an introducer sheath to the target site and then engaging the ostium of the vessel. A wire guide is fed through the guiding catheter and ostium where it is placed across the lesion in the vessel. Finally, a balloon catheter is introduced over the wire guide and positioned at the lesion to dilate the vessel. Increasingly more often, a stent is also placed following balloon dilatation to prevent restenoses of the lesion. One procedure for placing the balloon catheter at the treatment site is known as the "Push-Pull" Technique whereby the physician advances the balloon catheter through the guiding catheter ("push") while applying slight forward pressure to the latter. At the same time, an assistant holds the proximal end of the wire guide, providing gentle traction ("pull"). Care must be taken during the advancement of the catheter to avoid dislodging the wire guide from the treatment site. This is especially of concern during a renal procedure due to the relatively short length of the renal artery and the acute angle of the artery relative to the aorta.
The unique anatomy of the renal vessels presents difficulties when using existing wire guides for PTRA. Many physicians select wire guides developed for coronary procedures which are designed to facilitate negotiation of tortuous vessels and minimize trauma to small delicate coronary arteries. Because of their required flexibility, coronary wire guides usually lack the desired stiffness for PTRA. A stiffer wire guide permits better tracking by the catheter over the wire. However, a stiff wire guide can also subject the vasculature to forces during manipulation that are capable of perforating the vessel or injuring the ostial takeoff from the aorta into the renal vessel. The wire guide receives much of the up and down stresses during the procedure and transfers them to the vessel wall. These same stresses are often responsible for dislodging the distal end of the wire guide from the orifice, necessitating withdrawal of the catheter and reintroduction of the wire guide. If the wire guide enters the ostium of the vessel at the correct angle, the stresses are instead received by the catheter, thus protecting the fragile vessel. Furthermore, the typical stresses at that site during manipulation of a straight wire can also cause thrombus to shear from the vessel wall, often leading to an embolus and related serious complications.